This invention relates to chromatography and more particularly, it relates to an improved cartridge column for use in a chromatography system.
Traditionally, columns or use in chromatography systems, including liquid, gas or supercritical fluid chromatography, usually employ a stainless steel tube in which is provided a packing material or sorbent. The sorbent is selected in accordance with the intended use and usually is held in the tube by use of a frit provided at both ends. Compression end fittings are used to hold the frit in place and to connect the column to an injector and to a detector. The compression end fittings normally employ nuts and ferrules on the outside of the column to close it. Nuts and ferrules are used to screw or join the column to the injector or detector by capillary tubing. The fittings at the ends of the column have to be provided with tapered seats on the end fittings in order to provide or a high compression seal on the column tube and connection tubing. However, the end fittings, ferrules, nuts and tapered seats employed add significantly to the cost and bulkiness of the column. Also, because of the design and relatively large ferrules employed and to provide a high compression seal, tools or wrenches often have to be used to tighten the nuts, making installation inconvenient.
Because of the problems with conventional columns, more recently cartridge columns have been employed. Cartridge columns do not require the bulky compression fittings. Thus, the overall cost of the column is reduced and ease of installation and use is improved. One type of cartridge column is disclosed in U.S. Pat. No. 4,283,280. In this design, the outside of the cartridge is smooth, and fritted seals are pressed onto each end to hold the packing material in place. However, this type of cartridge requires a special holder to fit over the cartridge which adds greatly to its expense and inconvenience. The holder is reusable but is limited in use to the same length cartridge, and the holder obscures the column label. Another type of cartridge column design employs threads on the outside of the cartridge column. This permits the reuse of the end fittings when the cartridge column is replaced. Also, most cartridge systems, especially for HPLC, are too bulky with special fittings or holders to fit into many types of popular block heaters, requiring larger air ovens for temperature control.
In yet another design, instead of threads, a groove is employed on the cartridge column. However, this design requires the use of a special collar and end fittings which add to the cost of the columns. Most of these cartridges require tools or extra parts such as holders for installation in a high pressure system for example, where leak-free operation is critical to function.
Thus, it will be seen that there is still a great need for an inexpensive, easy-to-install cartridge column for use in chromatographic systems at low or high pressures. The present invention provides such a cartridge column.